Gold can't possibly be in a bubble. it's a measuring stick that has been manipulated by governments for decades. The rise in price that you are seeing is the market recognising the flaw in the system. I don't think that gold will drop below $1000 again. Ever!

Chinese/Indian lemmings running to their destruction. When they collapse under the weight of their junk investments, including investments in gold, their central banks will be selling this gold for $50 an ounce, but there will be very few buyers.

2 - The US is hit with another financial crisis. This time, there is no bailout. Banks fail and the money supply drops. Demand for dollars pushes gold price down.

3 - Stocks really take off next year. Dollars will retreat from gold into stocks.

4 - As zloj suggests, the catalyst could be foriegn. China and India have their own financial meltdowns. Demand for currency will push down gold prices around the world. In addition, more investment dollars will flee from gold for the -now cheap- investments overseas.

5 - Gold is simply overbought due to irrational panic. All it will take is a hole in the dike.

I'll be the first to admit that the first two are very unlikely. Options 3 and 4 are a bit more probable, and option 5 may be the most likely. Just a foolish guess.